This invention relates to a method of joining metal members and, more particularly, to a method of joining a plurality of electrically conductive members together.
In order to achieve the joining of metal members together, mechanical methods including caulking, pressure welding, and cladding; and welding methods including brazing, soldering and fusion; welding have been employed.
In the mechanical method, a great force is mechanically applied to the members to be joined. Accordingly it is necessary to provide materials high in ductility such as Ag-Ni and Ag which can sufficiently withstand plastic deformation. These materials are low in wear resistance and are liable to be molten at high temperature. Therefore, the method is limited to the manufacture of laminated conductors of relatively small size and capacity. Further, as to the caulking method, a resultant conductor caulking is low in current feeding performance. As the number of components is increased, the manufacturing cost is increased.
In the welding method, the low melting point alloy layer of the brazing material and the base material forms voids in the course of cooling. As the voids occupy 20 to 30% of the junction area, the thermal characteristic is lowered, and furthermore the mechanical strength is also lowered. Thus, the electrical conductor manufactured by this method is low in reliability. In addition, in the welding method, the flux and brazing material being used become colloidal, which is an obstruction to automation and labor-savings. Air pollution attributing to the fumes produced by the oxidation of cadmium included in the brazing material is a serious problem in manufacturing electrical contactors. In order to eliminate this difficulty, it is necessary to plate the junction surface with silver in advance, which results in an increase in the manufacturing cost.